Like I said, if it's the cause of concern, sleepless nights, and countless nightmares, go ask for the additive to be put in. However, just keep in mind that whenever any oil services are done to your differential, you will have to ask for the additive every time.
Not like you change your diff oil every 1k mile or anything ridiculous, but still something to keep in mind.
Personally, I like the noise. Reminds me that the M is an M.